1. Field of the Invention
The present invention generally concerns digital electronic cameras, and waterproof housings for cameras including digital electronic cameras.
The present invention particularly concerns the communication of (i) information, (ii) control and (iii) power across a watertight barrier, particularly such as may serve to protect an electronic instrument, most commonly a digital electronic camera, including when the instrument is immersed in water.
2. Description of the Prior Art
Relevant Previous Patents
A significant body of prior art concerning waterproof housings for conventional film cameras is substantially irrelevant to the present invention for several reasons. First, the housing or case for a conventional, non-electronic, camera must open for retrieval and replacement of the filmxe2x80x94as will prove to be unnecessary with a digital electronic camera. Second, since the camera""s case or housing will open, and required replacement of batteries is readily accomplished by physical substitution, no battery recharging need transpire through the case or housing.
The case and its waterproof seals can be, and often are, quite sophisticated in supporting the transmission of mechanical forces and adjustments as may attend, inter alia, adjustment of the camera""s focus and/or the actuation of its shutter. However, and although a digital electronic camera may have a focus adjustment and will have a shutter, these mechanisms can be electrically, as opposed to mechanically, actuated.
Accordingly, the present invention will prove more analogous to certain prior art underwater electronic devicesxe2x80x94including electronic imaging devices such as, inter alia, a video tape recorderxe2x80x94than to underwater film cameras. (Of course, even with a video tape recorder, a watertight enclosure will open for access to the videotape.)
In this regard, U.S. Pat. No. 3,952,190 to Perkins for an UNDERWATER STROBE FLASH UNIT concerns a method of waterproofing a strobe flash unit for use in underwater photography. A mold is formed and a strobe flash unit is mounted within the mold. Epoxy resin is poured into the mold to surround the strobe flash unit with the resin. The resin is then cured until it hardens, at which time the mold is removed from the epoxy resin and strobe flash unit. The resultant product is a strobe flash unit encapsulated in a transparent waterproof casing. Such encapsulation will be seen to be suitably employed in the present invention.
As regards the communication of power to a hand held underwater electronic imaging device, U.S. Pat. No. 4,009,419 to Ligman for a SAFETY CIRCUIT FOR VIDEO DIVER concerns an underwater diver who is provided with a video camera, light, and communications all of which is supplied with electrical current from the surface by a shipboard electrical circuit. The diver is protected from accidental excessive voltages and current by magnetically isolating the diver""s current from the shipboard current and by employing optical feedback to control the voltages for the diver. Additionally, a standby battery is employed to energize this equipment when the shipboard power fails. The entire shipboard power supply is contained in a waterproof box upon which is also mounted a video monitor and a video recorder, both secured in watertight fashion to the box. The present invention will be seen to involve the transmission of power into a waterproof enclosure, but not while the enclosure is immersed, and normally not while an electronic digital camera within the enclosure is in use.
The present invention will be seen to involve optical data transmission. U.S. Pat. No. 5,847,753 to Gabello, et al., for a CAMERA SYSTEM FOR SCANNING A MOVING SURFACE concerns a camera system utilizing a line scan (linear array) camera designed to scan a moving surface and subsequently to generate and to transmit a high quality digitized video signal over a long a distance by an optical fiber. The primary function of the system is: to scan a moving surface using a 2048 or a 1024 linear array; to condition and digitize the array analog video signal; and subsequently to transmit to a computer processing unit, without a noticeable loss in fidelity, the digitized video data over a long distance by means of an optical fiber connected to the camera and the computer processing unit. The system also functions to transmit both video signals and non-video information signals over a fiber optic link from the camera to the computer processing unit.
An Exemplary Modification of an Existing Digital Camera
The present invention will be seen to employ but very, very slightxe2x80x94substantially inconsequentialxe2x80x94physical and electrical modifications to an existing digital electronic camera. No modifications at all are required by the present invention in the personal computer, nor in the operating software, that are commonly used to recover digital images from the digital electronic camera. However, all these things are readily susceptible of modification, if required.
It is thus useful to consider the susceptibility of a digital electronic camera to electrical and/or physical modification. An example of modificationsxe2x80x94much more extensive than are required by the present inventionxe2x80x94to an existing digital camera to support of its use in a non-standard, space borne, environment is shown in a Stanford University student project.
An Exemplary Existing Digital Electronic Camera
The Logitech Fotoman Plus digital electronic camera is a 8-bit grayscale digital camera, capable of storing 32 JPEG compressed pictures in memory. Its specifications, according to Logitech, are as follows:
The camera dimensions are 16.8 centimeters (6.7 inches) by 8.1 cm (3.2 in) by 3 cm (1.2 in). The camera weight is 284 grams (10 ounces).
Camera image quality is 256 gray levels over 496xc3x97360 pixels, for an equivalent resolution of 120 dots per inch (120 dpi) over a photo approximately 4 in (12.7 cm) widexc3x973 in (8.9 cm) high.
The lens is fixed focus with a 8.5 millimeters (mm) focal length, f/4.5. The 35 mm camera equivalent focal length is 64 mm. Shooting range is 3 feet (1 meter) to infinity.
The camera""s equivalent film sensitivity is approximately ASA 200 without the neutral density filter, and approximately ASA 25 with the filter.
The camera""s electronic shutter speed is 40 milliseconds (xcx9c{fraction (1/30)}) with the flash, and 0.5 to 50 msec ({fraction (1/2000)} to {fraction (1/20)}) without the flash.
The flash guide number equivalent is 27 at ASA 200. The flash shooting range 3 ft (1 m) to 8 ft (2.5 m). The life of the flash is 10,000 flashes.
The image capacity of camera is 32 pictures in an image storage medium: namely, solid state (dram) memory with battery backup.
The image sensor type is a CCD (charge-coupled device). The raw image size is 179 kb (8 bits per pixel). Compressed image size varies with the image. Average compressed image size is 23 kb with 8:1 compression using the JPEG image compression method.
The adapter rings have a small end of 27 mm threaded outer diameter, and a large end of 37 mm threaded inner diameter.
The camera cable length is 6 ft. (2 m) of cable suitable for the camera""s RS423 serial interface (which is simply +/xe2x88x92 5v version of the more famous RS232 serial interface, which will be seen to be the type used in the preferred embodiment of the present invention).
The baud rate of the interface is 9.6 K baud receive, and 9.6K, 19.2K, 38.4K, 57.6K, of 115k baud transmit.
The main power source of the camera is two rechargeable nickel-cadmium batteries, AA size, 600 ma, 1.2 V. The time needed to charge these Ni-Cad batteries is 6 hours minimum. In estimating loss of charge in the Ni-Cad batteries assume that, at room temperature, the batteries lose about 20% of a full charge every time the camera takes one full load of photos (32 photos). The batteries lose about 15% of a full charge every time the camera goes 24 hours without recharging.
The battery charger has an output 12 vdc +4 v, xe2x88x922 v, 500 mah minimum. The polarity-positive pole is at center.
A memory power source is based on a 3 v lithium cell.
Camera operating temperature and humidity is 0 to 40xc2x0 C. at 95% humidity or less. Camera storage temperature and humidity is xe2x88x9240 to 50xc2x0 C. at 95% humidity or less.
An existing Logitech Fotoman Plus digital camera (the xe2x80x9cFotoman cameraxe2x80x9d) is modified by, among other things, placing it in a protective box. The capabilities of this digital camera include JPEG image compression, storage in DRAM of up to 32 496xc3x97360 images with 8-bit gray scale in compressed form. The compression results in a JPEG image size of about 23 Kb.
A serial link to the CPU, RS-232, is used to load into the Fotoman camera memory its operating software, to give it instructions, and to transfer back the camera status and full images.
The digital camera can be powered on/off, from the +5 V bus of the spacecraft. A voltage regulator and a bypass capacitor are used to replace the Ni-Cad batteries normally used to power the Fotoman Plus (see schematic) A lithium battery, used by the Fotoman to maintain the operating software in memory, is left in the camera.
2.2.2 Exemplary Previous Electrical Modifications to an Existing Digital Electronic Camera
In accordance with the present invention, connection will be made to the circuitry of a digital electronic camera. That a connection toxe2x80x94and more, rising to the level of actual modification ofxe2x80x94the circuitry of an existing digital electronic camera might be made is known.
For example, the aforementioned Fotoman Plus digital electronic camera was subjected to electronic modifications. The Fotoman Plus camera was already designed with appropriate digital communications interfaces without the need for any custom adapter. However, an external switch controlled by the on/off command from the CPU and voltage regulation had to be added. It was so added by wiring an existing RS423 serial interface from a bottom 6 electrodes already present in the camera. (With the lens on top, the six electrodes from left to right are: 1. Connection directly to the battery through a fuse, located in the camera, which is used to monitor battery level in manufacturing. A battery eliminator could be connected, but the fuse would have to be bypassed; 2. RS423 out; 3. Charge in (+12 V); 4. RS423 in; 5. Ground, used for both power and RS423; and 6. Unused.)
Next, a power regulation and switching circuit were designed to turn on the Fotoman camera if a xe2x80x9conxe2x80x9d signal was received from the CPU through the bus of the space satellite in which the modified camera was to be flown, and contained.
Finally, the flash had to be selectively electronically disabled by removing certain components off the PCB. (The components were C32, Q18, Q24, Q27, R94, and R93, as indicated on the printed circuit board of the camera.)
2.2.3 Exemplary Modifications to the Software-Based Interface and Control of an Existing Digital Electronic Camera
It will be seen to be one of the strengths of the present invention that no modification is needed to the firmware within the camera, nor the software within a connecting computer. It will be understood, however, that such minor modifications as might be required are well within the skills of a practitioner of the digital computer programming arts.
For example, the Fotoman Plus camera has a command set the detail nature of which is not of particular concern in the present application.
Using this instruction set software for control of the camera was modified in accordance with the space mission of the camera.
The Fotoman Plus camera software architecture is based on a boot code stored in the Fotoman Plus camera ROM. This main code stored in the Fotoman Plus camera RAM is known as FOTOWARE. This code operates the Fotoman Plus camera, performs the data compression, and manages the communications with an external computer through a serial link.
The Fotoman Plus camera software architecture is also based on an exploitation code, known as FOTOTOUCH, based on an external computer. This code contains a dialogue/acquisition segment, an executable named FOTOMAN.EXE, and an image processing segment.
Finally, the Fotoman Plus camera software architecture is also based a native mode communication program TERM permitting ASCII commandsxe2x80x94used in commanding the Fotoman Plus cameraxe2x80x94to be entered via a keyboard.
The camera modification plan called for a special version of the FOTOWARE that permitted programmed (i) disabling of the flash, (ii) manual setting of the exposure time, and (iii) control of the battery counter. The battery counter is a model of the battery maintained by the FOTOWARE, which does not measure any physical quantity from the batteries. However, the battery counter must be above a certain level, before the Fotoman can take a picture.
However, if the camera batteries are removed and replaced, the on=board software assumes that the replacement batteries are uncharged. As the power circuitry for the digital camera replaces the batteries, on power up, the counter will read zero and the camera will not be able to take a picture. By controlling the counter, the programmer(s) can change the erroneous indication of insufficient power, and can take a picture immediately. Flash control is recommended, as the flash will be physically disabled.
FOTOTOUCH or any other standard image manipulation package can be used in the ground station to view and process the images, which are downloaded in standard JPEG format.
2.2.4 Exemplary Use of a Modified Existing Digital Electronic Camera
The present invention deals with a digital electronic camera modified for underwater use. It is known to attempt to modify a digital electronic camera for a specific applications environment, to wit: the space borne application of the Fotoman Plus camera.
In that application full new software supports camera dialogue/acquisition with the spacecraft CPU, and interfaces the camera into the main control module of the spacecraft. This software performs the following tasks: 1. turning on and off the Fotoman Plus; 2. uploading FOTOWARE from the PROM into the Fotoman Plus RAM at a given time; 3. sending orders to take pictures to the Fotoman; 4. Request and receiving status, contact, and image inventory information; and 5. retrieving pictures from the Fotoman, to be stored in the CPU, which will be sent at a later time to the ground station.
These tasks can be performed using the 16 commands set of provided in the Native Mode Toolkit.
Typical tasks for the modified FotoMan executable under software control are to 1. take a picture at a given time (using the on-board clock); and 2. download a picture #n stored in CPU memory.
For further explanation see the Fotoman Plus camera User""s Guide (a basic user""s guide) and the Fotoman Plus Camera Native Mode Toolkit (logical interface specifications) supplied by Logitech Inc., Fremont Calif. 94555. See also JPEG documentation and source code at ftp site: ftp.uu.net /graphics/jpeg file jpegsrc.v4.tar.Z; and general information on image compression from the list at FAQ of the Internet newsgroup at comp.compression.research.
The present invention contemplates a weathertight and watertight digital electronic device, particularly a digital camera, that is designed to operate both on land and underwater to great depths. The camera is preferably hermetically sealed, and is thus impervious to contamination both from the atmospherexe2x80x94such as may arise from wind-blown sand and smokexe2x80x94and from water and like fluids, including during full immersion including at great depths and pressures.
The hermetic sealing is realized by an encapsulating housing, or case. This housing is totally without any passage of (i) electrical wires or cables conducting electrical current, or of (ii) mechanical plungers or actuators imparting mechanical force(s), through its wall(s). Thus when the housing is described as xe2x80x9chermetically sealedxe2x80x9d in this specification then this term means more than xe2x80x9cairtightxe2x80x9d, but, as will be seen, less than xe2x80x9cimmune to external influencexe2x80x9dxe2x80x94as are both dictionary definitions of the word xe2x80x9chermeticxe2x80x9d. The concept of xe2x80x9chermetic sealingxe2x80x9d of a digital electronic device, or camera, in accordance with the present invention is this: there are no seals, nor any points of substantially different vulnerability to breach, within the entire housing. Indeed, the housing may be molded as a monolithic block. Its surface may be fashionedxe2x80x94at least so far as regards possibilities and potential for ingress or egress to the digital camera or other electronic device contained insidexe2x80x94as a continuum, meaning by dictionary definition something of which no distinction of content may be affirmed except by reference to something else. In simplest terms, once sealed shut the housing is solid, and like as a monolith without any physical passages whatsoever within its surface.
Nonetheless that the watertight digital electronic camera of the present invention is hermetically sealedxe2x80x94or possibly because it is so hermetically sealedxe2x80x94its housing, and all necessary electrical and digital electrical communication with the camera, are economical to manufacture. This economy results primarily because, as explained above, there are absolutely no physical passages though the housing of the camera, nor are any expensive waterproof fittings employed. Indeed, in one of its embodiments the housing of the camera is formed by completely encapsulating the camera, and some modest auxiliary electronics, within a solid block of, preferably, plastic during a potting process.
The hermetically sealed watertight digital electronic camera so constructed is characterized by having all necessary (i) signal, (ii) control and (iii) power communication with the camera transpire by and through radiation links that pass through the housing of the camera.
Regarding (i) signal communication, the communication of image data from the camera to the exterior of its transparent case is preferably via a radio or, more preferably, an optical link, most preferably an infrared optical link.
Regarding (ii) control communication, the watertight digital electronic camera so constructed is further characterized in that communication of an actuation signal to the shutter of the camera preferably transpires via a magnetic link. In the preferred embodiment a trigger circuit based on a Hall-effect sensor or a reed switch, and located interior to the sealed case, produces an electrical signal suitable to actuate the camera""s existing shutter circuit whenever a small permanent magnet exterior to the case is brought into proximity, normally by manual movement in a simple sliding mechanism in a manner suggestive of a standard shutter release.
Regarding (iii) power communication, the watertight digital electronic camera so constructed is still further characterized in that the camera has, quite conventionally, a rechargeable source of power, normally a battery. This power source is, however, quite unconventionally recharged via an inductive coupling. In the preferred embodiment of the camera an oscillating, alternating current (a.c.), electromagnetic field external to the camera housing is inductively coupled into (i) an inductive coil internal to the housing. Also internal to the housing, (ii) a bridge rectifier rectifies the alternating current induced in the inductive coil to produce a direct current, and (iii) a regulating and charging circuit conditions this direct current into power to charge the rechargeable power source.
As a still further major aspect of the present invention, the housingxe2x80x94which is normally formed quite snug to the camera and its auxiliary electronic circuitsxe2x80x94may be filled with an optically-transparent electrically-dielectric liquid. The housing may even be formed by potting: solidifying a liquid polymer that extends into all regions and volumes of the housingxe2x80x94including inside the camera properxe2x80x94into a solid block of optically-transparent electrically-dielectric plastic. This construction, which leaves the enclosed volume of the housing substantially entirely devoid of gas, permits that the waterproof camera may be used at great depths of at least a mile, and may be non-destructively subjected to correspondingly great hydrostatic pressures. Any necessary preset to the lens system of the camera to account for the differing indexes of refraction of air and of the potting plastic is contemplated.
1. An Underwater Digital Electronic Camera System
Therefore, in one of its aspects the present invention will be recognized to be embodied in a waterproof digital electronic camera system suitable for use underwater. The system includes (i) a digital electronic camera, and (ii) a converter, in (iii) an enclosure.
The (i) digital electronic camera has a digital electrical signal interface for downloading image information from the camera.
The (ii) converter converts signals upon the digital electrical signal interface to optical or to radio frequency signals.
The (iii) enclosure hermetically seals water and air tight both (i) the digital electronic camera and (ii) the converter. The enclosure is transparent in at least an area of lens of the digital electronic camera so that pictures may be taken through the enclosure. The enclosure is additionally transparent to radiation so that either an optical, or a radio frequency, signal output of the converterxe2x80x94which signal contains image information xe2x80x94is communicable exterior to the camera.
The (i) digital electronic camera typically has a serial digital electrical signal interface, and most commonly an RS-232 interface, thus making that (ii) the converter is converting signals upon this serial digital electrical signal interface to serial optical, or radio frequency, signals. The preferred converter in particular includes (a) an RS-232 to TTL signal converter converting RS-232 serial digital electrical signals to Transistor-Transistor Logic (TTL) serial digital electrical signals, and (b) an encoder-decoder converting the TTL electrical signals to electrical signals that are suitably encoded so as to be converted to optical or radio frequency signals for further transmission. The converter further has (c) an electrical-to-optical, or an electrical-to-radio, signal converter for converting the encoded electrical signals to optical or radio signals, and for transmitting the optical or radio signals through the at least one radiation-transparent area of the enclosure.
Conversion need not be realized in a converter having these exact functional or physical sections (a)-(c). For example, in one embodiment of the invention an RS-232(C) electrical signal to and from the camera goes directly to a (spread-spectrum) radio frequency transceiver module for bi-directional communication outside the camera. Moreover, in many embodiments of the camera system some or all of these three sections (a)-(c) of the converter may be hard to locate, and distinctly identify. For example, all three sections (a)-(c) may be combined in an optical, or in a radio, transceiver. It will be recognized by a practitioner of the electromagnetic communication arts that there are diverse ways of communicating electrical signals upon an electronic device, particularly a digital electronic camera, bi-directionally through a radiation-transparent window located in a case encapsulating the device (the camera).
Further in the preferred system of the invention, the digital electronic camera conventionally has a shutter circuit for activating the shutter, to which shutter circuit electrical connection may suitably be made. Meanwhile, the overall system additionally includes a trigger circuit. This trigger circuit is within the enclosure and is electrically connected to the shutter circuit of the digital electronic camera. It serves to respond to some stimulus external to the enclosure so as to produce responsively thereto an electrical signal which, as and when supplied to the shutter circuit, will activate the shutter of the digital electronic camera.
The trigger circuit may be implemented in several different variants. A Hall-effect sensor responsive to a magnetic field can be used to produce a signal output, with an amplifier amplifying this signal output for application to the shutter circuit as the electrical signal responsively to which the shutter circuit will activate the shutter of the digital electronic camera. Triggering of the Hall-effect sensor may be realized by the simple expedient of manually moving a permanent magnet, external to the enclosure, into physical proximity to the Hall-effect sensor that is within the enclosure.
Alternatively, the trigger circuit may be based on a reed switch, or sensor, that is also responsive to a magnetic field to gate an electrical signal responsively to which the shutter circuit will activate the shutter of the digital electronic camera.
Still further in the preferred system of the invention, the digital electronic camera has, as is again conventional, a rechargeable power source, normally a battery, for providing power to at least the digital electronic camera and also, in the case of the system of the invention, the converter. In this eventuality the overall system preferably further includes a charging circuit, also within the enclosure, for converting some stimulus external to the enclosure to power suitable to recharge the rechargeable power source. The stimulus is preferably an oscillating, alternating current (a.c.), electromagnetic field. Accordingly, the preferred charging circuit includes (i) an inductive coil in which alternating current is induced by an oscillatory magnetic field external to the enclosure, (ii) a bridge rectifier rectifying the alternating current of the inductive coil to produce a direct current, and (iii) a regulating and charging circuit conditioning the direct current into power to charge the rechargeable power source.
The enclosure of the digital electronic camera and its associated auxiliary electronics is structurally simple and inexpensive, but functionally sophisticated. In one preferred variant the camera and the converter (and any other incorporated features such as the trigger circuit and/or the charging circuit) are entirely potted in an optically clear dielectric material. This optically clear dielectric potting material is preferably drawn from the group consisting essentially of plastic and any of hydrocarbon liquids, mineral oil, polyester resin and clear silicone rubber. The optically clear dielectric potting material is more preferably polycarbonate plastic and ethyl alcohol.
In a first variant of this potting, discussed further in section 3, below, the potting may extend into the interior volumes of the camera (and anything else, such as the inductive coil), so that, ultimately, the enclosure contains only solid masses, and is devoid of any gas whatsoever.
In another, second, variant the (potted, or otherwise sealed) enclosure contains both solid and liquid masses, only, and there is still essentially no gas whatsoever within the enclosure nor within the camera that is within the enclosure. In this variant the liquid is an optically clear dielectric, and thus interferes with neither the optical functions of the camera nor the electrical functions of the camera and of the converter.
In yet another, third, variant the (potted, or otherwise sealed) enclosure may contain solid and/or liquid masses, but with a slight remaining volume between the elements of a compound lens, and/or between the lens and the (clear) camera case, in which is captured gas, normally air. This third variant camera may be quite easily constructed, typically requiring no alteration, even to the modest extent of de-focusing, of the optical system of the (digital electronic) camera. To such extent as the xe2x80x9cgas pocketxe2x80x9d is well protected, the camera may function at considerable pressures, and depths ranging to, typically, hundreds of feet. However, at the very greatest depths of the ocean, the gas pocket represents a compressible fluid, and its presence may undesirably physically distort the remaining structure of the encapsulated camera even if it does not lead to failure by rupture.
2. An Encapsulated Waterproof Digital Electronic Camera System
Therefore, in another of its aspects the present invention will be recognized to be embodied in a waterproof digital electronic camera where the optics and electronics of the camera are permanently within a solid mass of optically clear dielectric material, and where the camera contains essentially no gases whatsoever. By this construction the camera may suitably be immersed to great depth within the ocean without crushing.
In one variant of construction the digital electronic camera is potted inside and out to be within a solid block of optically clear dielectric material, preferably plastic and more preferably polycarbonate plastic.
In another variant of construction the digital electronic camera is within an optically clear liquid dielectric material, the camera and its liquid being held within a liquid-tight exterior case that is itself optically clear in at least a region where an image is received through the case and into a lens of the camera. The preferred liquid is a liquid hydrocarbon, and is more preferably ethanol.
3. An Underwater Watch
As a further extension of the broad concepts of the present invention a completely sealed underwater watch can be made by encasing a digital watch, including its electronics and battery, inside a clear plastic slab. The settings of the watch can be changed using the hall-effect magnetic proximity switches described above. The watch battery can also be recharged as previously described for the waterproof digital electronic camera.
Alternatively, the watch can simply be fitted with a single battery which will last for several years; the nominal life of the watch. (An optional photovoltaic array permits recharging.) The watch is economical yet operable at great depths and pressures since it is entirely embedded in plastic and there are no, or substantially no, air spaces inside.
These and other aspects and attributes of the present invention will become increasingly clear upon reference to the following drawings and accompanying specification.